import { base, keyName } from "w3c-keyname"
import { Plugin } from "../state"

// declare global: navigator

const mac =
  typeof navigator != "undefined" ? /Mac/.test(navigator.platform) : false

function normalizeKeyName(name) {
  let parts = name.split(/-(?!$)/),
    result = parts[parts.length - 1]
  if (result == "Space") result = " "
  let alt, ctrl, shift, meta
  for (let i = 0; i < parts.length - 1; i++) {
    let mod = parts[i]
    if (/^(cmd|meta|m)$/i.test(mod)) meta = true
    else if (/^a(lt)?$/i.test(mod)) alt = true
    else if (/^(c|ctrl|control)$/i.test(mod)) ctrl = true
    else if (/^s(hift)?$/i.test(mod)) shift = true
    else if (/^mod$/i.test(mod)) {
      if (mac) meta = true
      else ctrl = true
    } else throw new Error("Unrecognized modifier name: " + mod)
  }
  if (alt) result = "Alt-" + result
  if (ctrl) result = "Ctrl-" + result
  if (meta) result = "Meta-" + result
  if (shift) result = "Shift-" + result
  return result
}

function normalize(map) {
  let copy = Object.create(null)
  for (let prop in map) copy[normalizeKeyName(prop)] = map[prop]
  return copy
}

function modifiers(name, event, shift) {
  if (event.altKey) name = "Alt-" + name
  if (event.ctrlKey) name = "Ctrl-" + name
  if (event.metaKey) name = "Meta-" + name
  if (shift !== false && event.shiftKey) name = "Shift-" + name
  return name
}

// :: (Object) → Plugin
// Create a keymap plugin for the given set of bindings.
//
// Bindings should map key names to [command](#commands)-style
// functions, which will be called with `(EditorState, dispatch,
// EditorView)` arguments, and should return true when they've handled
// the key. Note that the view argument isn't part of the command
// protocol, but can be used as an escape hatch if a binding needs to
// directly interact with the UI.
//
// Key names may be strings like `"Shift-Ctrl-Enter"`—a key
// identifier prefixed with zero or more modifiers. Key identifiers
// are based on the strings that can appear in
// [`KeyEvent.key`](https://developer.mozilla.org/en-US/docs/Web/API/KeyboardEvent/key).
// Use lowercase letters to refer to letter keys (or uppercase letters
// if you want shift to be held). You may use `"Space"` as an alias
// for the `" "` name.
//
// Modifiers can be given in any order. `Shift-` (or `s-`), `Alt-` (or
// `a-`), `Ctrl-` (or `c-` or `Control-`) and `Cmd-` (or `m-` or
// `Meta-`) are recognized. For characters that are created by holding
// shift, the `Shift-` prefix is implied, and should not be added
// explicitly.
//
// You can use `Mod-` as a shorthand for `Cmd-` on Mac and `Ctrl-` on
// other platforms.
//
// You can add multiple keymap plugins to an editor. The order in
// which they appear determines their precedence (the ones early in
// the array get to dispatch first).
export function keymap(bindings) {
  return new Plugin({ props: { handleKeyDown: keydownHandler(bindings) } })
}

// :: (Object) → (view: EditorView, event: dom.Event) → bool
// Given a set of bindings (using the same format as
// [`keymap`](#keymap.keymap), return a [keydown
// handler](#view.EditorProps.handleKeyDown) that handles them.
export function keydownHandler(bindings) {
  let map = normalize(bindings)
  return function (view, event) {
    let name = keyName(event),
      isChar = name.length == 1 && name != " ",
      baseName
    let direct = map[modifiers(name, event, !isChar)]
    if (direct && direct(view.state, view.dispatch, view)) return true
    if (
      isChar &&
      (event.shiftKey ||
        event.altKey ||
        event.metaKey ||
        name.charCodeAt(0) > 127) &&
      (baseName = base[event.keyCode]) &&
      baseName != name
    ) {
      // Try falling back to the keyCode when there's a modifier
      // active or the character produced isn't ASCII, and our table
      // produces a different name from the the keyCode. See #668,
      // #1060
      let fromCode = map[modifiers(baseName, event, true)]
      if (fromCode && fromCode(view.state, view.dispatch, view)) return true
    } else if (isChar && event.shiftKey) {
      // Otherwise, if shift is active, also try the binding with the
      // Shift- prefix enabled. See #997
      let withShift = map[modifiers(name, event, true)]
      if (withShift && withShift(view.state, view.dispatch, view)) return true
    }
    return false
  }
}
